Since August 3 (eight sessions) the Dow has traded as high as
13,223.01 and as low as 13,094.96 for a range of 128 points, or
0.98 percent. In percentage terms that is the narrowest
8-day trading range since at least 1950. I couldn't
check back any further than 1950, but I think the point is clear.
No conviction, no volume, truly the dog days of summer on Wall
Street!

And on August 17, there was this from Robert Hum...

And finally the clincher: Monthly S&P trading volume over the
last 10 years. Total collapse.

Bloomberg

September should be grand: ECB, Jobs Report, the Fed, and
(perhaps) the return of a little volume.